View Full Version : stacking boulders?/making ncloth deform around objects?

04 April 2008, 12:12 AM
As you read this you will realize I have quite a bit to learn about dynamics...I really could use some help please!

I've spent 5 days trying to stack about 1000 boulders on top of one another in the shape of a pyramid. The camera will be getting really close to this pile so I need for it to not have a ton of interpenetration amongst the boulders. As well, I need to get it done ASAP. I've tried the following to accomplish this:

1) Made a collision cone container and I tried using instanced geometry, but didn't realize that instanced geometry doesn't collide. I saw a work around with using radial fields, but I couldn't figure out how to make that work.

2) Next I tried using a cone passive body and making the boulders rigid bodies. I tried laying down a level of boulders at a time to sort of stack them up. It works, but if I want it to finish calculating before December then this isn't an option. The issue with the calculations taking so long is that Maya still wants to calculate the previous levels I have laid down. So then my calculation times increases exponentially and it's out of control.

3) Right now I have taken the first level of the boulders that I had calculated as rigid bodies and deleted the rigid bodies and history and exported the geometry out. I've taken it into a new scene and I was thinking that maybe I could drop a piece of nCloth on top of the first level and let the cloth deform around the shapes and into the crevices of the boulders. Then I could take that and create a passive rigid body out of it and collide the next row of boulders on top of it. My thinking is that this would let me stack the boulders higher without having the rigid bodies calculate the previous levels. Make sense?

So, my question, how can I make the nCloth sort of adhear itself to the boulders? I need for it to deform as much as possible to the boulders and crevices around them.

Or, if anyone has another way of approaching this please let me know!

04 April 2008, 02:34 AM
Dude(tte), I would get some decent hi res images of a stack of boulders, preferably 4 files (you can also clone images using photoshop. Setup 4 sides of the pyramid and projection map the files onto all sides. Make a copy of each file and convert to BW, add a little blur, then use these files as displacement maps on the shaders. Then convert the displacements to poly and either instance rocks onto the surface through surface emission or make the surface live and use PaintFX to brush boulders on for randomness and where any closeups are required.

04 April 2008, 08:00 AM
Thanks for the suggestion. I actually was able to find a different solution via a friend and we were able to get it to quickly work using rigid bodies. I know more than anyone that "Maya", "rigid bodies", and "quickly" are 3 words that never should be in the same sentence. However, this solution actually worked beautifully and when get a chance I will post some examples.

For a brief explanation as to what I did... I was able to get my rigid body solution to work by running the PhysX engine in Maya 8.5, baking out the simulation (300 frames), and then bringing it into Maya 2008. The beautiful part was that we weren't quite sure how to actually get the simulation out of 8.5. However, the software was never written for 2008 since they stopped making it so when we brought it into 2008 we realized that Maya didn't know what to do with the file or data so it just gave us our simulation on keyframes. Not 100% the ideal solution, but it worked brilliantly for my situation. The best part of it all is that I was able to get the simulation calculated and baked in 1 hour using about 1000 boulders as rigid bodies. Each boulder having roughly 40 faces. That would have taken Maya 10 years to calculate and PhysX ran it in an hour. Since I only needed the last frame of the sim (the final pile) the rendertime on this is pretty quick.

I really wish this engine was still being made. I believe they originally had it for free on their site? I would have easily paid for it. You can still find the downloads and plugins on their site for free if you are a member:

04 April 2008, 06:50 PM
an often overlooked solution for rigid bodies is realflow. It has a really nice rigid body solver which works fast for lots of rigid bodies. I am currently running several sims with over 10k rigids in each one. Of course by "fast" I mean hours, not days.


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